During the course of a study on surface coatings, the Applicant was concerned with polymer compositions. Following this work, compositions of particular interest for surface coatings were developed, these compositions containing at least one thermoplastic polymer which is usually amorphous or of low crystallinity, and at least one epoxy resin modified by at least one aromatic polyamine.
The present invention concerns the use of these compositions to coat metal or other surfaces, for example for receptacles or conduits. These compositions are particular suitable for protecting surfaces, in particular metal surfaces. These compositions are used to coat conduits and pipelines in particular, especially metal conduits and steel pipelines.
Pipelines are metal tubes, often formed from steel, essentially used in wells to transport crude oil and natural gas, but any type of fluid could be transported by such pipelines. The internal surface of the pipeline is corroded by the transported fluid. When the transported fluid is oil, the sulphur-containing compounds contained in the oil are the main causes of the corrosion. When drilling offshore, the external surface of the pipeline is also corroded by sea water.
The principal problem with depositing a polymer on a metal surface, for example the external and/or internal surface of a pipeline, for example of steel, is the behaviour of the polymer when it is subjected to heat stress. Even if the oil is cooled before transporting it, the pipeline is often heated to a temperature of about 50xc2x0 C. to 200xc2x0 C. by contact with hot oil. Certain polymers, for example polypropylene, tend to distort and no longer adhere to the metal once the temperature exceeds 130xc2x0 C. Other polymers, such as polyetherimides or polysulphones, adhere at high temperatures but their application temperature (at which it is deposited on the metal) is higher, about 360xc2x0 C. Further, metals, in particular steelxe2x80x94frequently used in the production of pipelinesxe2x80x94, may undergo phase distortions from a temperature of about 250xc2x0 C., and certain of their mechanical and physical properties can be altered.
In addition, good adhesion of the polymer at a higher temperature enables the oil to be transported without the need to cool it, or at least it only needs to be cooled to a lesser extent. At a relatively high temperature, oil is less viscous and therefore easier to transport.
The use of the polymer compositions of the present invention overcomes the above disadvantages; in particular, such use produces pipelines with a coating with good adhesion, good stiffness, and good resistance to sea water. Further, the properties of the polymer compositions used are only slightly altered when these compositions are aged.
The polymer compositions used contain at least one thermoplastic polymer, usually having a high glass transition temperature and preferably being amorphous or of low crystallinity, usually selected from the group formed by polysulphones, polyetherimides and polyphenylene ethers and at least one epoxy resin modified by at least one aromatic polyamine containing at least two primary amine groups in its molecule; preferably, sterically hindered polyamines are selected, i.e., they contain at least one alkyl substituent containing 1 to 12 carbon atoms located alpha to one of the amine groups. In the remainder of the description, the polyamines described above are termed xe2x80x9caromatic polyaminesxe2x80x9d.
Preferably, the polymer compositions used contain at least one thermoplastic polymer in an amount of about 15% to 98% by weight, more preferably 30% to 70% by weight, with respect to the total composition weight, and at least one epoxy resin modified by at least one aromatic polyamine in an amount of about 2% to 85% by weight, preferably about 30% to 70% by weight, with respect to the total composition weight.
The term xe2x80x9cpolysulphonexe2x80x9d may be the source of an ambiguity. The first polymer of commercial importance with a base unit containing a sulphone group xe2x80x94SO2xe2x80x94 was, the polymer sold by AMOCO under the trade name UDEL. Because of this, this particular polysulphone is often designated by the generic term polysulphone. In the present description, the term xe2x80x9cpolysulphonexe2x80x9d is used in its generic sense, and not just the limiting sense of a UDEL type polysulphone.
The polysulphones used in the polymer compositions of the invention are preferably aromatic polysulphones, more preferably UDEL type polysulphones, RADEL A polysulphone type polyether-sulphones sold by AMOCO, and RADEL R polysulphone type polyphenylene sulphones also sold by AMOCO.
The polyetherimides used in the polymer compositions are preferably ULTEM type polyetherimides sold by General Electric Plastics.
The polyphenylene ethers used in the polymer compositions are preferably PPE 800 type polyphenylene ethers sold by General Electric Plastics.
As used in the present invention, the thermoplastic polymers can be used alone, mixed with each other or mixed with other polymers such as aromatic polyetherketones or polyphenylene sulphides. Polymer compositions comprising aromatic polyetherketones contain about 1% to 50% by weight thereof with respect to the total weight of thermoplastic polymers. Polymer compositions comprising polyphenylene sulphides contain about 1% to 50% by weight thereof with respect to the total weight of thermoplastic polymers.
The epoxy resins modified by at least one aromatic polyamine, preferably sterically hindered, used in the polymer compositions are epoxy resins formed from at least one polyepoxide containing at least two epoxy groups in its molecule and at least one aromatic polyamine containing at least two primary amine groups in its molecule, and at least one alkyl substituent containing 1 to 12 carbon atoms located alpha to one of the amine groups, the mole ratio of the amine to the epoxy being such that each amine group corresponds to 1.6 to 2.6 epoxy groups.
The aromatic polyamines are selected for their low reactivity and for their non toxic nature.
The epoxy resin can be selected from the group formed by the following commercially available resins: the diglycidylether of bis-phenol-A or bis-phenol F, bis-phenol formol resin, phenol-novolac resin, cycloaliphatic resins, tri- or tetrafunctional resins, resins formed from triglycidylether-isocyanurate and/or triglycidylether-cyanurate and/or triglycidyl-cyanurate and/or triglycidyl-isocyanurate or mixtures of at least two of these resins.
The epoxy resins obtained from the epoxy resins cited in U.S. Pat. No. 4,921,047 can also be used in the present invention.
The aromatic polyamines used in the polymer compositions include a first series of aromatic amines comprising a single aromatic ring such as 3,5-diethyl-2,4-dinitrotoluene, 3,5-diethyl-2,6-diaminotoluene and mixtures of these two isomers. Usually, a mixture of these two isomers generally known as DETDA is used.
In a second series of amines used, amines containing at least two aromatic rings can be considered, these two aromatic rings generally being connected to each other by a bivalent linear or branched hydrocarbon residue containing 1 to 18 carbon atoms. These two aromatic rings are either connected via a bivalent alkyl group or are connected one to the other via a bivalent linear or branched hydrocarbon residue containing 6 to 18 carbon atoms and containing an aromatic ring.
The amine can also contain at least one substituent selected from the group formed be fluorine, iodine, bromine and chlorine. It preferably contains at least two alkyl substituents, each being alpha either side of an amino group.
When the two aromatic rings are connected via a bivalent alkyl residue, this residue is preferably a methylidene group which is non substituted or substituted by at least one radical selected from alkyl radicals and halogenoalkyl radicals containing 1 to 3 carbon atoms. As an example, this alkyl residue is selected from the group formed by the methylidene group, the isopropylidene group, the halogenoisopropylidene groups, and the hexafluoroisopropylidene group. In this case, the amine is preferably selected from the group formed by:
4,4xe2x80x2-methylene-bis(2,6-dimethylaniline) or M-DMA;
4,4xe2x80x2-methylene-bis(2-isopropyl-6-methyl-aniline) or M-MIPA;
4,4xe2x80x2-methylene-bis(2,6-diethylaniline) or M-DEA;
4,4xe2x80x2-methylene-bis(2,6-diisopropylaniline) or M-DIPA; and
4,4xe2x80x2-methylene-bis(3-chloro-2,6-diethylaniline) or M-CDEA.
Of these amines, 4,4xe2x80x2-methylene-bis(2,6-diethylaniline) and 4,4xe2x80x2-methylene-bis(3-chloro-2,6-diethylaniline) are of particular interest.
When the amine contains two aromatic rings which are connected to each other via a bivalent hydrocarbon residue which may or may not be substituted, containing 6 to 18 carbon atoms and containing an aromatic ring, it is preferably selected from the group formed by:
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dimethyl-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diethyl-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dipropyl-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diisopropyl-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dimethyl-3-chloro-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diethyl-3-chloro-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dipropyl-3-chloro-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diisopropyl-3-chloro-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dimethyl-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diethyl-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dipropyl-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dimethyl-3-chloro-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diethyl-3-chloro-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dipropyl-3-chloro-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diisopropyl-aniline); and
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diisopropyl-3-chloro-aniline).
The polymer compositions of the present invention can also contain catalysts which are active for the reaction between the epoxy resins and the sterically hindered aromatic polyamines. The most frequently used active catalysts are imidazoles, tertiary amines and boron trifluoride based complexes. Additives selected from the group formed by antioxidants, pigments, adhesion promoters, heat stabilisers and organic, mineral or metallic fillers can also be added.
These polymer compositions are preferably prepared without a solvent in the molten state at a temperature of about 100xc2x0 C. to 250xc2x0 C., preferably about 150xc2x0 C. to 200xc2x0 C. This preparation is preferably carried out using a mixer such as a twin screw extruder. In this preferred mode of preparation, the epoxy resins, aromatic polyamines and any additives are introduced into the mixer in the form of a premix to which the thermoplastic polymer is added; each reactant can also be separately introduced into the mixer via different inlet zones or via a single inlet zone. It is also possible to mix the thermoplastic polymers and epoxy resins first, then to acid the aromatic polyamine. It is also possible to introduce the aromatic polyamine into the mixer into a zone close to the zone for recovering the polymer composition.
Once the mixture has been produced, the polymer composition is formed then preferably cured. Curing generally consists of heating the composition to a temperature of about 200xc2x0 C. to 250xc2x0 C., for example, for a period of about 10 minutes to 12 hours. It is preferably carried out in an oven.
Layers of polymer compositions can thus be deposited on different types of conduits, in particular on pipelines produced from metal, more particularly from steel. Internal and external coatings can be formed. Different application methods have been studied. Of the possible application methods, dusting and extrusion deposition methods are preferred. The thickness of the polymer composition layers formed is generally about 10xc3x9710xe2x88x926 m (10 micrometers) to 1xc3x9710xe2x88x922 m (1 centimeter), preferably about 50xc3x9710xe2x88x926 m (50 micrometers) to 5xc3x9710xe2x88x923 m (5 millimeters).
Uses for polymer compositions for coating surfaces with multi-layers have also been tested. Up to 5 superimposed layers have been produced. Preferably, 2 to 4 layers were superimposed in the tests.
Thus one polymer composition layer containing at least one thermoplastic polymer and at least one epoxy resin modified by at least one polyamine was deposited on the metal, in particular on steel or on steel coated with an anti-corrosion primer and/or an adhesion promoter. Deposits on other materials, in particular on other polymers, were also studied.
Uses for polymer compositions for coating surfaces with multi-layers were also tested. Thus one (or more) layers of polymer composition containing at least one thermoplastic polymer and at least one epoxy resin modified by at least one polyamine had deposited on it a layer of a polymer composition containing at least one thermoplastic polymer and at least one epoxy resin modified by at least one aromatic polyamine, the layers containing identical or different thermoplastic polymers in identical or different proportions.
A layer of a polymer composition containing at least one thermoplastic polymer and at least one epoxy resin modified by at least one aromatic polyamine has also had deposited on it reactive polymers with good adhesion to the layers onto which they are deposited, such as polymers with one or more reactive functions for example epoxy, alcohol, amine, acid, anhydride, thiol or polyolefins with functions which react with epoxy or polar functions, or a modified polyolefin P1 containing at least one succimide ring substituted on the nitrogen by a reactive group, said ring being supported either by the main chain or by the side chain. It is also possible to use the product resulting from the reaction of this modified polyolefin with at least one polyepoxide containing at least two epoxy groups in its molecule.
This polyolefin P1 can be defined as being the product resulting from the reaction of at least one polyolefin with at least one compound containing a maleimide ring substituted on the nitrogen by a reactive group with formula xe2x80x94Rxe2x80x94 (X)n where X represents a reactive group, n represents a number equal to 1 or more and R is a residue containing at least one carbon atom. Usually, n equals 1 and in this case the compound containing a maleimide ring used in the present invention is represented by the formula (I) below: 
The reactive group xe2x80x94X is normally selected from a hydroxyl group, a carboxyl group, a carboxamide group, a carboxylic acid halide group, a thiol group, a thio-carboxyl group, an amine group, a halogen, an epoxy group and an esterified carboxyl group where the ester portion comprises a reactive group. When a plurality of groups xe2x80x94X are present, they can be identical or different.
The reactive group xe2x80x94X is usually selected from groups which can react with epoxy functions by oxirane ring opening. Usually, compounds containing a reactive group selected from the carboxyl group, the carboxamide group, an acid halide group, for example a carboxylic acid halide group, are used. The carboxyl group is preferred.
The group xe2x80x94Rxe2x80x94 is normally selected from saturated or unsaturated, substituted or non substituted aliphatic hydrocarbon groups, and substituted or non substituted aromatic groups. Generally, non substituted groups are preferred and usually the groups contain at least one aromatic ring. An example of a group which is often used is a benzene group ortho, meta or para to the nitrogen atom and to a reactive group xe2x80x94X. Usually, the para or meta form is used.
The polyolefins used to form this layer can be any polyolefin which is well known to the skilled person. Preferably, polyolefins obtained from at least one unsaturated monomer containing one or more unsaturated bonds is used, usually selected from the group formed by ethylene, propene, butenes and norbornenes. Thus these polyolefins can be formed by homopolymerisation or copolymerisation of at least two monomers.
These layers of polymer compositions with one or more reactive functions as defined( above are generally about 1xc3x9710xe2x88x926 m (1 micrometer) to 500xc3x9710xe2x88x926 m (500 micrometers) thick, preferably about 100xc3x9710xe2x88x926 m (100 micrometers) to 400xc3x9710xe2x88x926 m (400 micrometers) thick.
A preferred use for the polymer compositions containing at least one thermoplastic polymer and at least one epoxy resin modified by at least one aromatic polyamine for coating the external surfaces of conduits consists of forming the following multi-layer. At least one first layer containing at least one thermoplastic polymer and at least one epoxy resin modified by at least one aromatic polyamine is directly deposited on the conduitxe2x80x94or onto the conduit after depositing, an anti-corrosion primer and/or an adhesion promoter. On this layer, a second layer of the polymer defined above is deposited, having one or more reactive functions and with good adhesion to the first layer. Finally, this system has deposited on it a layer of commercially available polymer selected from the group formed by polyolefins, such as polyethylenes and polypropylenes, and with good compatibility with the second layer: as an example, a layer of commercially available polyethylene will be deposited on a layer of modified polyethylenexe2x80x94with at least one reactive function.
This last layer can be in the form of a solid or it can be cellular. Further, it is generally about 10xe2x88x923 m (1 millimeter) to about 10xc3x9710xe2x88x922 m (10 centimeters) thick.
More generally, at least one polymer composition containing at least one thermoplastic polymer and at least one epoxy resin modified by at least one aromatic polyamine can be used as an intermediate layer between a surface and a layer of a thermoplastic polymer composition containing at least two distinct polymers at least one of which is a polymer comprising at least one reactive function, and at least one modified polyolefin containing at least one succimide ring substituted on the nitrogen by a reactive group, said ring being supported either by the main chain or by the side chain.
Of the methods for depositing these multi-layer coatings, one preferred method consists of depositing a layer of a polymer composition containing at least one thermoplastic polymer and at least one epoxy resin modified by at least one aromatic polyamine on a support at the application temperature for said polymer composition, then depositing on this layer a further layer of a polymer composition selected from those defined above at its application temperature. After depositing each layer it can be cured at about 200xc2x0 C. to 250xc2x0 C., for a period of about 10 minutes to 12 hours. Curing can also be carried out after depositing all of the layers onto the coating. Preferably, curing is carried out after depositing all of the layers, this implementation thus achieving good cross linking of the layers between each other.
The present invention also concerns surface coatings comprising at least one thermoplastic polymer preferably selected from the group formed by polyetherimides, polysulphones and polyphenylene ethers and at least one epoxy resin modified by at least one aromatic polyamine containing at least two primary amine groups in its molecule, the epoxy resin being formed from at least one polyepoxide containing at least two epoxy groups in its molecule and the molar ratio of the aromatic polyamine to the epoxy resin being such that each amine group corresponds to 1.6 to 2.6 epoxy groups.
The invention also concerns multi-layer surface coatings comprising at least two identical or different layers in which at least one first layer contains at least one thermoplastic polymer preferably selected from the group formed by polyetherimides, polysulphones and polyphenylene ethers and at least one epoxy resin modified by at least one aromatic polyamine as defined above, and at least one second layer which is identical or different to said first layer, preferably selected from the group formed by the reactive polymers described above and the modified polyolefins described above, or a mixture of these two product types. In the present description, in the case of coatings comprising at least two layers, the term xe2x80x9cfirst layerxe2x80x9d does not imply that this layer is that which is in direct contact with the surface to be coated.
The following examples illustrate the invention without limiting its scope.
The polymer compositions in the following examples were prepared using a twin screw extruder from CLEXTRAL; this extruder comprised a plurality of positions for introducing the reactants to be mixed. For these examples, the epoxy resin and aromatic polyamine were first mixed; this mixture will hereinafter be termed the xe2x80x9cpremixxe2x80x9d. The thermoplastic polymers were introduced via an inlet zone and the premix was introduced via a further inlet zone. The rate for the premix was constant, and was introduced using a gear pump. In contrast, the thermoplastic polymers were introduced using a gravimetric metering hopper which enabled the rate of the thermoplastic polymers to be varied, and thus polymer compositions with different modified resin/thermoplastic polymer ratios could be produced.
The thermoplastic polymers were introduced into the extruder""s inlet zone at the end opposite to the zone for recovering the polymer composition. The temperature in this inlet zone was 100xc2x0 C. They were then entrained in a second zone where the temperature was 150xc2x0 C. and into which the premix was introduced. These reactants were then entrained by the twin screw extruder, with the temperature inside the extruder slowly increasing to attain 185xc2x0 C. and the extruder outlet.